My hair started thinning back when I was in my late twenties. I'm in my forties now and it's still noticably thinning and getting very grey, and my beard (when I have one) is black, ginger, grey and white so who knows what's going on?
I don't mind though - the older I get, the more comfortable I feel in my skin.
I think we're far too worried about ageing these days - my wife and I wouldn't dream of dyeing our hair or covering up our age - I've got more grey hair than my mum!